examples/example4/example4.cpp

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#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <FCam/N900.h>
#include <FCam/AutoExposure.h>

// Select the platform
namespace Plat = FCam::N900;
// namespace Plat = FCam::F2;

/***********************************************************/
/* Autoexposure                                            */
/*                                                         */
/* This example shows how to request streams and deal with */
/* the incoming frames, and also uses the provided         */
/* autoexposure routine.                                   */
/***********************************************************/
int main(int argc, char ** argv) {

    // Make a sensor
    Plat::Sensor sensor;
    
    /* Shot */
    FCam::Shot stream1;
    // Set the shot parameters
    stream1.exposure = 50000;
    stream1.gain = 1.0f;

    // Request an image size and allocate storage.
    stream1.image = FCam::Image(640, 480, FCam::UYVY);

    // Enable the histogram unit.
    stream1.histogram.regions = 1;
    stream1.histogram.region[0] = FCam::Rect(0, 0, 640, 480);
    
    // We will stream until the exposure stabilizes.
    int cnt = 0;        // # of frames streamed
    int stable_cnt = 0; // # of consecutive frames with stable exposure.
    float exposure;     // exposure for the current frame
    float lastExposure; // exposure for the previous frame
    
    FCam::Frame::Ptr frame;

    do {
    // Update lastExposure
    lastExposure = exposure;
    
    // Ask the sensor to stream with the given parameters.
    sensor.stream(stream1);
    
    // Retrieve a frame
    frame = sensor.getFrame();
    assert(frame->shot().id == stream1.id); // Check the source of the request.
    
    // Call the autoexposure algorithm. It will update stream1.
    autoExpose(&stream1, frame);
    
    // Calculate the exposure used
    exposure = stream1.exposure * stream1.gain;
    
    // Increment stable_cnt if the exposure is within 10% of the previous one.
    if (cnt++ > 0) {
        stable_cnt = fabs((exposure - lastExposure) / lastExposure) < 0.1f ?
        stable_cnt + 1 : 0;
    }
    } while (stable_cnt < 5); // Terminate when stable for 5 frames.
    
    // Order the sensor to stop streaming.
    sensor.stopStreaming();
    printf("Processed %d frames until stable for 5 frames!\n", cnt);
    printf("Final exposure: %f us", exposure);
    
    // There may still be shots in the pipeline. Consume them.
    while (sensor.shotsPending() > 0) frame = sensor.getFrame();

    // Write out file if needed.
    if (argc > 1) FCam::saveJPEG(frame, argv[1]);   
    
    // Check that the pipeline is empty.
    assert(sensor.framesPending() == 0);
    assert(sensor.shotsPending() == 0);
}

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